The present invention relates generally to invasive apparatus and methods for treating a patient, and specifically to facilitation of percutaneous insertion of devices into a patient""s body.
The use of catheters to inject, sample, drain, biopsy and implant various instruments in a body has developed into a highly sophisticated area of medical and veterinary practice. Seldinger, for example, developed a commonly-used technique for introducing a catheter into the vascular system of a patient. The equipment required to perform this basic technique includes a thin wall introducer needle, a wire guide, and a plastic preformed catheter. A simple puncture is performed, in conjunction with x-ray films for guidance, and access is gained to any part of the body via the cardiovascular system.
U.S. Pat. No. 4,581,025 to Timmermans, which is incorporated herein by reference, describes the use of a longitudinally-split catheter, which allows easy removal of the sheath from a patient""s body.
U.S. Pat. No. 4,921,479, to Grayzel, which is incorporated herein by reference, describes a catheter sheath with a longitudinal seam. The seam includes a longitudinal slit, which allows enlargement of the sheath""s diameter to accommodate a catheter inserted therein. It further allows the wall of the sheath to fit snugly around the catheter to afford guidance of the catheter into a blood vessel.
U.S. Pat. No. 5,057,092 to Webster, which is incorporated herein by reference, describes a catheter sheath, having a flexible plastic inner wall and a braided reinforcing mesh surrounding the inner wall. The reinforcing mesh allows the catheter sheath to be thinner than would be possible using, for example, the catheter described in the Timmermans patent, because a non-reinforced, thin-walled catheter would be likely to tear in some circumstances. Nevertheless, the catheter sheath described in the Webster patent is relatively difficult to remove from the patient""s body.
In general, the current state of the art appears to have the disadvantage of either having relatively weak, easily torn and easily removable thin-walled catheter sheaths, somewhat stronger, bulkier, thick-walled sheaths that are easily removable, or reinforced thin-walled sheaths, which are relatively difficult to remove from the body.
It is an object of some aspects of the present invention to provide improved methods and apparatus for inserting a catheter sheath into a patient""s body.
It is a further object of some aspects of the present invention to provide improved methods and apparatus for removing a catheter sheath from a patient""s body.
In preferred embodiments of the present invention, a partially-braided sheath has one or more longitudinal sections. A physician typically inserts the sheath into a vessel of a patient, and guides a catheter through the sheath to a destination inside the patient""s body. For some applications, the physician then withdraws the sheath from the vessel, while generally maintaining the catheter in place. Preferably, there are one or more respective seams between adjacent edges of the sections of the sheath, which bind the sections together prior to and during use of the sheath. Each of the seams preferably comprises a longitudinal slit, which enables the sheath to be easily split by the physician, upon removal of the sheath from the body.
Advantageously, the partial braiding of the sheath typically increases the resistance to kinking and overall mechanical strength thereof, such that insertion of the sheath into the vessel is relatively easy. By contrast, the prior art describes two major classes of catheter systems. The first class includes a reinforced and easily-inserted sheath, which is relatively difficult to remove from the body, such as that described in the above-cited U.S. Pat. No. 5,057,092. The second class includes a relatively soft and flexible sheath, which is difficult to insert, but has a longitudinal slit to make the sheath easy to remove, as described in the above-cited U.S. Pat. No. 4,921,479. Preferred embodiments of the invention described herein combine the advantages of both types of prior art catheter sheaths, yet minimize the disadvantages of each type of prior art sheath. The braiding of parts of the catheter sheath adds mechanical strength so as to allow easy insertion of a thin-walled sheath which is unlikely to tear, while the one or more longitudinal seams allow easy splitting of the sheath upon its removal from the vessel.
There is therefore provided, in accordance with a preferred embodiment of the present invention, apparatus for insertion into a lumen of a body of a subject, including a sheath, the sheath including:
at least one section which is reinforced by braiding, the section extending longitudinally along at least a portion of the sheath; and
at least one section which is substantially not reinforced, extending longitudinally along at least the portion.
Preferably, the at least one section which is substantially not reinforced includes a seam, which is adapted to open responsive to application of lateral tension thereto.
For some applications, the sheath is adapted to be inserted into a blood vessel.
There is also provided, in accordance with a preferred embodiment of the present invention, a method for removing a sheath from a lumen of a body of a subject, including:
withdrawing the sheath from the lumen so that a segment of the sheath is outside the body, the sheath having at least one longitudinal section thereof which is reinforced by braiding, and at least one longitudinal section thereof which is substantially not reinforced; and
applying tension to the non-reinforced section, so as to split the sheath longitudinally at the non-reinforced section.
Preferably, applying the tension so as to split the sheath includes splitting the sheath along a seam of the at least one longitudinal section which is substantially not reinforced.